I was told to start timing from the beginning but a private tutor I worked with. I thought it was a ludricous suggestion because what was the use of timing, if I didn't know what I was doing to begin with.
When I took the PS class, the recommendation was to do the first 10 hw questions untimed, the next 10 untimed, but noticing how much time it took to do all 10, the final set was to be done, timed according to LSAT specs. After a few weeks of lessong, when I had a grasp of the basic concepts, then I started to do timed sections and tests. I found that worked best for me